I. Field of the Invention
The present invention relates generally to trackside railway car handling equipment for positioning railcars along a track for loading or unloading operations. More particularly, the present invention relates to train positioning systems that are operable either as indexers or progressors and which operate against the bogey frames of rail cars.
II. Related Art
Freight-hauling railway cars need to be precisely positioned proximate freight or cargo handling equipment during loading and unloading operations. Freight in the form of bulk cargo such as grain is typically loaded or unloaded with reference to stationary freight handling equipment such as chutes and conveyor equipment situated at fixed locations above or in pits beneath a specific portion of the track. Railcars for transporting grain or other such finely divided dry bulk agricultural commodities may be covered and designed with a plurality of spaced bottom discharge hopper bins or chutes accessing the main cargo storage volume. The chutes are closed by capstan-operated rack and pinion bottom closure gate systems.
In the loading and discharge operations, a connected engine roughly positions one end of a string of cars to be loaded or unloaded beneath or above the appropriate equipment at the desired fixed location. Because locomotives are not well suited for precisely positioning individual cars or even strings of cars along a railroad track, positioning devices known as train movers or positioners are located at fixed stations along the track. The positioning devices generally employ heavy pushing members known as railcar-engaging “dogs” to move the cars into position.
Positioning devices are generally classified in the industry as “indexers” or “progressors”. Indexers may employ dogs carried by a pair of carriages operating along indexer tracks on built-in guideways located on opposite sides of associated track rails. Indexers are designed so that the carriages and associate dogs on both sides of the track are coordinated to operate together in unison to engage and move a car or string of cars along the track. Thus, in indexer type bogey frame-engaging positioning devices, both dogs of a pair of dogs spaced on opposite sides of the track are caused to engage the bogey frame during the same stroke to thereby provide a balanced force by pushing against both of the spaced sides of the truck bogey frame simultaneously.
Progressors designed to operate against bogey frames also operate along rails in built-in guideways on the outside of each of the spaced rails of a track with dogs that operate along each of the guideways spaced along the track. Rather than operating simultaneously against both sides of a bogey frame to move a car or string of cars, the dogs of a progressor are operated alternately, to sequentially engage a bogey frame so as to “hand off” the car or string of cars alternating between dogs on opposed sides of the track.
Using either type system an entire string of connected cars may be advanced with precision and loaded or unloaded, one car at a time. As with the indexer system, the progressor can be stopped at any point in the operating cycle when the desired position is reached.
Operation of car handling equipment in each of the modes described above has certain advantages and either may be desirable depending on operational circumstances and conditions. As indicated, operation as an indexer advantageously provides a balanced side-to-side force on the bogey frame and enables the total force of two dog carriage systems to be applied at once so that heavier loads may be moved. This also enables a balanced force to be applied against the bogey frames of lightly loaded cars which avoids a possible tipping situation which may occur when force is applied to one side only. However, because indexers operate the dogs together, after a power stroke, both dogs must be retracted and the next bogey frame found before the next power stroke can be started. Operating both dogs together on the power stroke necessarily slows the speed of progression. Progressor type operation can provide multiple power strokes in rapid succession by alternating carriage operation in a hand-off fashion, however, the applied force is limited to that of a single dog carriage and the force of that dog is operated against only one side of the bogey frame.
Heretofore, such railcar handling equipment has been constructed as dedicated to operation either as an indexer or a progressor and it would provide a distinct advantage and answer a definite need in the art if such a system could handle railcars in either manner.